1. Field of the Invention
The present invention relates to a semiconductor device including a circuit constituted by thin film transistors (hereinafter referred to as xe2x80x9cTFTsxe2x80x9d). Particularly, the present invention relates to a structure of an electro-optical device typified by a liquid crystal display device and an electronic equipment incorporating such an electro-optical device as a part.
Incidentally, in the present specification, the term xe2x80x9csemiconductor devicexe2x80x9d indicates any devices functioning by using semiconductor characteristics, and all of electro-optical devices, semiconductor circuits, and electronic equipments are semiconductor devices.
2. Description of the Related Art
In recent years, an attention has been paid to a technique for constructing a thin film transistor TFT by using a semiconductor thin film (its thickness is several hundreds to several thousands nm) formed on a substrate having an insulating surface. The thin film transistor is widely used for an electronic device such as an IC or an electro-optical device, and particularly as a switching element of an image display device, its development has been hastened.
For example, in a liquid crystal display device, an attempt to apply the TFT to any electric circuits, such as a pixel matrix circuit for controlling each of pixel regions arranged in matrix form, a driver circuit for controlling the pixel matrix circuit, and a logic circuit (a processor circuit, a memory circuit, etc.) for processing a data signal from the outside, has been made.
Under the present circumstances, although a TFT using a noncrystalline silicon film (amorphous silicon film) as an active layer has been put to practical use, a TFT using a crystalline silicon film (a polysilicon film, a polycrystalline silicon film, etc.) is necessary for an electric circuit required to have further high speed operating performance, such as a driver circuit or a logic circuit.
For example, as a method of forming a crystalline silicon film on a glass substrate, techniques disclosed in Japanese Patent Unexamined Publication No. Hei. 7-130652 and No. Hei. 8-78329 by the present applicant are well known. The techniques disclosed in these publications use a catalytic element for promoting crystallization of an amorphous silicon film, so that formation of a crystalline silicon film superior in crystallinity is made possible by a heat treatment at 500 to 600xc2x0 C. for about 4 hours.
Particularly, the technique disclosed in Japanese Patent Unexamined Publication No. Hei. 8-78329 is such that crystal growth almost parallel to a substrate surface is made by applying the above technique, and the present inventor et al. refer to a formed crystallized region especially as a side growth region (or a lateral growth region).
However, even if a driver circuit is constructed by using such TFTs, such a state has not been attained that required performance is completely satisfied. Under the present circumstances, it is impossible especially to construct with conventional TFTs a high speed logic circuit requiring an extremely high speed operation of megahertz to gigahertz.
As described above, for the purpose of realizing a system-on-panel having a built-in logic circuit, development of a quite novel material which has not existed has been required.
The present invention has been made to respond to such a request, and an object of the invention is to provide a structure of a TFT with extremely high performance, which can construct such a high speed logic circuit as has not been capable of being fabricated with a conventional TFT, and a method of fabricating the same.
Moreover, in the present invention, an improvement has been made on a pixel matrix circuit. Specifically, the invention provides a structure for forming a storage capacitor capable of securing large capacity with a small area, and a method of fabricating the same.
Another object of the invention is to provide an electro-optical device having high reliability by forming each circuit of the electro-optical device typified by an AM-LCD with a TFT having a suitable structure according to a function.
According to the construction of the invention disclosed in the specification, there is provided a semiconductor device, characterized by comprising:
a source region, a drain region, and a channel formation region formed between the source region and the drain region, the respective regions being formed on an insulating surface;
a gate insulating film formed to be in contact with at least the channel formation region; and
a wiring formed to be in contact with the gate insulating film;
wherein a part of the source region and the drain region includes an element for promoting crystallization of silicon.
According to the construction, it is characterized in that the wiring includes at least one layer containing a kind of element selected from the group consisting of tantalum, molybdenum, tungsten, titanium, chromium, and silicon as its main ingredient.
According to the construction, it is characterized in that a part of the source region and the drain region includes an element or plural kinds of elements selected from the group consisting of nickel, cobalt, palladium, germanium, platinum, iron, and copper at a concentration of 1xc3x971019 atoms/cm3 or more.
Further, according to the construction of the invention, there is provided a semiconductor device including a driver circuit and a pixel matrix circuit formed on a same substrate, characterized in that a thickness of a dielectric of a storage capacitor included in the pixel matrix circuit is smaller than a thickness of a gate insulating film of a pixel TFT included in the pixel matrix circuit.
According to the construction, it is characterized in that the dielectric of the storage capacitor included in the pixel matrix circuit is formed through at least a thermal oxidation step.
According to the construction, it is characterized in that one of electrodes of the storage capacitor is a semiconductor film, and the one electrode includes an element selected from the group consisting of nickel, cobalt, palladium, germanium, platinum, iron, and copper at a concentration of 1xc3x971019 atoms/cm3 or more.
According to the construction, it is characterized in that the one electrode includes an element in group 15 at a concentration of 5xc3x971018 to 1xc3x971020 atoms/cm3.
According to the construction, it is characterized in that the thickness of the gate insulating film of the pixel TFT is 50 to 200 nm, and the thickness of the dielectric of the storage capacitor is 5 to 50 nm.
According to the construction, it is characterized in that the pixel TFT includes an active layer, an insulating film being in contact with the active layer, and a wiring being in contact with the insulating film,
the active layer includes a channel formation region, and a source region and a drain region formed at both sides of the channel formation region, and
a part of the source region and the drain region includes an element selected from the group consisting of nickel, cobalt, palladium, germanium, platinum, iron, and copper at a concentration of 1xc3x971019 atoms/cm3 or more.
According to the construction, it is characterized in that a low concentration impurity region is provided in at least one of a portion between the channel formation region and the source region, and a portion between the channel formation region and the drain region.
According to the construction of the invention to realize the structure, there is provided a method of fabricating a semiconductor device including a driver circuit and a pixel matrix circuit on a same substrate, characterized by comprising:
a first step of forming a semiconductor layer on the substrate by using a catalytic element;
a second step of selectively adding an element in group 15 to the semiconductor layer;
a third step of collecting the catalytic element by a heat treatment into a region where the element in group 15 is added;
a fourth step of forming an insulating film on the semiconductor layer;
a fifth step of removing a part of the insulating film to expose a part of the active layer;
a sixth step of forming a thermal oxidation film on the exposed part of the active layer;
a seventh step of forming a wiring on the insulating film and the thermal oxidation film;
an eighth step of forming a side wall at a side of the wiring;
a ninth step of adding an element in group 15 to the active layer while using the wiring and the side wall as masks;
a tenth step of removing the side wall;
an eleventh step of adding an element in group 15 to the active layer while using the wiring as a mask;
a twelfth step of adding an element in group 13 after a resist mask is formed on a region which becomes an NTFT; and
a thirteenth step of carrying out a treatment for activating the elements in group 13 and group 15 added to the active layer.
Further, according to the construction of the invention, there is provided a method of fabricating a semiconductor device including a driver circuit and a pixel matrix circuit on a same substrate, characterized by comprising:
a first step of forming a semiconductor layer on the substrate by using a catalytic element;
a second step of forming an insulating film on the semiconductor layer;
a third step of selectively adding an element in group 15 using a mask to the semiconductor layer;
a fourth step of removing a part of the insulating film using the mask to expose a part of the active layer;
a fifth step of collecting the catalytic element by a heat treatment into a region where the element in group 15 is added;
a sixth step of forming a thermal oxidation film on the exposed part of the active layer;
a seventh step of forming a wiring on the insulating film and the thermal oxidation film;
an eighth step of forming a side wall at a side of the wiring;
a ninth step of adding an element in group 15 to the active layer while using the wiring and the side wall as masks;
a tenth step of removing the side wall;
an eleventh step of adding an element in group 15 to the active layer while using the wiring as a mask;
a twelfth step of adding an element in group 13 after a resist mask is formed on a region which becomes an NTFT; and
a thirteenth step of carrying out a treatment for activating the elements in group 13 and group 15 added to the active layer.
According to the construction, it is characterized in that a part of the active layer includes at least a region which becomes a storage capacitor of the pixel matrix circuit.